Attentions when grinding cutter:(Applicable reference for the milling by brazing tools)
There is a big difference between thermal expansion coefficient of ultra micro-grain quality carbide and cutter body, and there is also a big difference between the conductivity of ultra micro-grain quality carbide and cutter body. As far as the cutter head is concerned, if the temperature increases too fast during the grinding, the surface temperature will increase quickly, but the temperature of the inner ultra micro-grain quality carbide, due to its conductivity, doesn't increase together with the surface temperature, so a temperature grads occurs between the inner side and surface of ultra micro-grain quality carbide blade. Thermal expansion on each temperature layer is different, so it will produce very large internal stress area. When this stress is large to a certain extent, it will cause the cutter head to crack along the temperature difference area or lower cutting property. During the grinding, the cutter head changes as the above, but the cutter body's thermal deformation will occur due to the characteristic of its materials during the rough grinding. When they reach a certain temperature, stress area begin to form on the surface. The faster the temperature decreases, the larger, the stress. When this stress is larger than what the cutter head can bear, the cutter head will crack or lower property.
Besides, there is a big difference between the thermal expansion coefficient of cutter body material and cutter head material and there is also a big difference between the deformation extent during the cooling. Therefore, a shear stress layer occurs between the cutter head's grinding surface and cutter head's inner material, and the expansion speed with surface produces a big difference, so a shear surface occurs at the dividing surface of different expansion speed. The stress of this surface is substantial so that crack will occur or the cutting property will be lowered. |